1. Technical Field
The invention relates to a device for linearly moving a cluster of control elements vertically into and out of the core of a nuclear reactor suitable for use when the cluster belongs to a set of two coaxially movable clusters fulfilling different functions.
2. Prior art
Providing such sets makes it possible to improve fine control, power adjustment, compensation of fuel burn-up and shut down of a nuclear reactor. Different set arrangements have been proposed, including sets in which one of the clusters is formed of so-called "black" elements having a very high neutron absorption and the other cluster is formed of "grey" elements. The cluster of "black" elements is lowered into the core of the reactor for causing and maintaining shut down. A motion device may be provided which is partially common to the clusters (French 2,106,373). It has also been proposed to associate a separate device with each cluster (French 2,537,764). But none of the prior arrangements allows full freedom of movement of one of the clusters, whatever the endmost positions occupied by the other cluster except at the expense of complex mechanisms.